one which in many mining districts involves considerations of practical importance, since a large supply would necessitate water or steam power. It has been found that two cells having an electromotive force of about two volts each will in this process suffice; if preferred, however, a very small dynamo machine can be used. In connection with the electro-motive force it is requisite to use, it may be observed that an amalgam of sodium containing only a small quantity of this metal would, when constituting a positive element in conjunction with a lead negative and on an aqueous electrolyte, give an opposing electro-motive force of less than three volts. Such an amalgam could therefore be obtained under an electro-motive force of about four volts. The electrical resistance in the circuit constituted by the apparatus being very small, no electrical power is wasted. When water constitutes the electrolyte, as in Barker's system, then the electro-motive force required to obtain a given current would be very much greater than that above specified. The conditions assured under this process appear to be all that can be required, while the amalgams obtained are those most calculated to preserve the "quickness" and prevent the "sickening" of the mercury. Mr. Molloy has designed a special form of amalgamating machine to be used in conjunction with the above process, and with or without the aid of water. By the employment of this machine, each particle of the ore is slowly rolled in the quickened mercury for from fifteen to thirty or more seconds. When the extent of the gold and silver mining industries is considered, and when it is borne in mind that a considerable percentage of the precious metal present in the ore is, in the ordinary process of extraction, lost through defective amalgamation--due to insufficient contact with the mercury or to a total absence of contact, as in the case of float gold--it is obvious that the introduction of any system obviating such loss is a matter of very great importance to those who are interested in the above mentioned industries. We expect shortly to hear of the practical introduction on a large scale of Mr. Molloy's process, and we look forward with interest to the results which may be obtained from it.--_The Engineer_. * * * * * TREATMENT OF ORES BY ELECTROLYSIS. By M. KILIANI.